Method and device for cooling a mass of a substance

ABSTRACT

The present invention relates to a method and a device for cooling a mass of a, for example, meat-, tissue-, vegetable- and/or fruit-containing substance in a container ( 2 ), in particular a mixer, blender or mill ( 3, 4 ), using liquefied nitrogen (N 2 ) which is supplied in the lower region of the container ( 2 ) at a constant working pressure via at least one nozzle. The method according to the invention and the device according to the invention are distinguished in that, during the cooling process and/or in stoppage times, the nitrogen is briefly supplied to the nozzle ( 7 ) or, via the latter, into the container ( 2 ) by means of at least one pressure pulse which is increased in relation to the working pressure. The pulsed supply of pressurized nitrogen blows blocked and/or iced-up nozzles (7) free again and thus advantageously ensures a more reliable operation of cooling a mass of a substance. The present invention is suitable, in particular, for use in foodstuff technology.

[0001] The present invention relates to a method and a device forcooling a mass of a, for example, meat-, tissue-, vegetable- and/orfruit-containing substance in a container, in particular a mixer,blender or mill, using liquefied nitrogen (N₂) which is supplied in thelower region of the container at a constant working pressure via atleast one nozzle.

[0002] Generic methods and devices are known, for example, from EP 0 978697 A1 or WO 98/57196 which likewise deal with the known problem thatsometimes tough foodstuffs, such as meat-, tissue-, vegetable-, and/orfruit-containing products, often cause clogging in devices, such asmixers, blenders or mills, and are difficult to process any further. Inthis respect, it is known to make the mass brittle, for example bycooling with liquid nitrogen, so that clogging is reduced and furtherprocessing, for example into hamburgers, chicken nuggets, vegetableburgers, fruit pouches or the like, becomes easier.

[0003] The mass is preferably cooled with liquid nitrogen by uniformpenetration. For this purpose, rotating blade elements are arranged inthe container, which mix, blend, knead and/or grind the mass of asubstance. Liquefied nitrogen is simultaneously supplied in the lowerregion of the container at a constant working pressure via at least onenozzle. Depending on the substance to be mixed, after about 2 to 60minutes the mass acquires a consistency which allows easier furtherprocessing.

[0004] However, cooling processes of this kind have not always proceededreliably in the past. Thus, it was to be observed that the nozzlesprojecting in the lower region of the container repeatedly becomeblocked and/or iced up individually. As a result of the impaired supplyof liquid nitrogen, the duration of the cooling process became up to 50%longer in a disadvantageous way. Moreover, the nozzles had to undergocleaning, and this was possible usually only in stoppage times and aftera sometimes complicated conversion of the plant.

[0005] The object of the present invention is to specify a method and adevice which ensure reliable operation for cooling a mass of asubstance. In particular, simple cleaning of nozzles, even within theduration of a cooling process, is to become possible.

[0006] This object is achieved by means of a method for cooling a massof a substance, having the features according to Patent Claim 1, and bymeans of a device, in particular for carrying out the method, having thefeatures according to Patent Claim 6. Advantageous developments andrefinements, which may be used individually or in combination with oneanother, are the subject-matter of the respective subclaims.

[0007] The method according to the invention for cooling a mass of a,for example, meat-, tissue-, vegetable- and/or fruit-containingsubstance in a container, in particular a mixer, blender or mill, usingliquefied nitrogen (N₂) which is supplied in the lower region of thecontainer at a constant working pressure via at least one nozzle, isdistinguished in that, during the cooling process and/or in stoppagetimes, the nitrogen is briefly supplied to the nozzle or, via thelatter, into the container by means of at least one pressure pulse whichis increased in relation to the working pressure. The pulsed supply ofpressurized nitrogen blows blocked and/or iced-up nozzles free again andthus advantageously ensures a more reliable operation of cooling a massof a substance.

[0008] At working pressures of, for example, between 1.5 and 3.5 bar,preferably between 2 and 3 bar, in particular 2.5 bar, according to theinvention the individual pressure pulse is preferably more than 4 timesthe working pressure in the case of, for example, slightly tough masses,preferably more than 6 times the working pressure in the case of, forexample, partly stuck-up and partly iced-up nozzles and, in particular,more than 8 times the working pressure in the case of, for example,severe icing-up of the nozzle, that is to say about 16 to 22 bar,preferably about 18 to 20 bar, in particular about 19 bar.

[0009] Operating reliability can be further increased if pressure pulsesare not generated solely when blockage or icing-up has occurred, butalso at regular time intervals, preferably every 4 to 6 minutes, inparticular every 5 minutes. This sometimes advantageously avoids theneed for means for observing and readjusting the process andadvantageously makes it possible to resort to experimental values ormakes manual regulation of the process necessary at most towards itsend.

[0010] Preferably, according to the invention, the pressure pulses aregenerated as follows:

[0011] liquid nitrogen which is under working pressure is enclosedhermetically in a storage region to which heat energy can be supplied;

[0012] as a result of the absorption of heat energy, part of the liquidnitrogen evaporates;

[0013] by virtue of different volumes of gaseous and liquid nitrogen,the pressure in the closed storage region rises;

[0014] when a desired set pressure value is reached, liquid nitrogenalone or a mixture of liquid and gaseous nitrogen is released in apulsed manner.

[0015] The use of nitrogen as a working and pressure fluidadvantageously makes it possible to construct and maintain genericplants less expensively, as compared with plants comprising specialcleaning devices and/or process management means.

[0016] The device according to the invention, in particular for carryingout the above-described method, for cooling a mass of a, for example,meat-, tissue-, vegetable- and/or fruit-containing substance in acontainer, in particular a mixer, blender or mill, using liquefiednitrogen (N₂) which can be supplied in the lower region of the containerat a constant working pressure via at least one nozzle, isadvantageously distinguished by means for generating at least onepressure pulse which is increased in relation to the working pressureand by means of which liquid and/or gaseous nitrogen can be supplied tothe nozzle or, via the latter, into the container during the coolingprocess and/or in stoppage times.

[0017] Preferably, according to the invention, the device comprises ahermetically lockable storage region, in which liquid nitrogen canpartially evaporate by the supply of heat energy, so that, by virtue ofdifferent volumes of gaseous and liquid nitrogen, the pressure in theclosed storage region rises until a desired set pressure value isreached and liquid nitrogen alone or a mixture of liquid and gaseousnitrogen can be released in a pulsed manner.

[0018] The storage region may be arranged essentially vertically orhorizontally and be installed in series or in parallel in a supplysystem. A horizontally arranged storage region which is part of a supplyline preceding the nozzle is preferred. Such a storage regionadvantageously allows a controlled pressure build-up by the separationof liquid and gaseous nitrogen into two regions, if appropriate by meansof a diaphragm, and the release of liquid nitrogen alone or of a mixtureof liquid and gaseous nitrogen, that is to say the highest possiblevariance of pressure pulses.

[0019] Preferably, according to the invention, the nozzle containspolytetrafluoroethylene (PTEF) which is advantageously suitable for usein foodstuff technology, in particular owing to low adhesive forces, alow heat capacity and conductivity and, in general, its inertcharacteristic.

[0020] For the further avoidance of sticking and icing-up, a nozzle isproposed, which has on the fluid-outlet side a conical aperture angle αof between 4° and 12°, preferably of between 6° and 10°, in particularof 8°, and which advantageously makes it easier to carry out anyblowing-out which is necessary.

[0021] Alternatively or additionally to this, a nozzle with a surfacewhich is located on the fluid-outlet side is proposed, which is designedto match with an imaginary spatial surface which is formed by arotatable or revolving mixing element arranged in the container of thedevice, the distance of the spatial surface formed by the mixing bladesfrom that surface of the nozzle which is located on the fluid-outletside being less than 5 mm, preferably less than 3 mm, in particular lessthan 1 mm, as a result of which, advantageously, slight deposits ofmass, in particular in the flow duct of the nozzle, or incipienticing-up are from time to time stripped away mechanically.

[0022] For the further avoidance of blocked nozzles, it is proposed thatthe nozzle project into the container at an angle of inclination β ofbetween 4° and 12°, preferably of between 6° and 10°, in particular ofless than 8°.

[0023] The device preferably comprises, furthermore, means forregulating the continuous and/or pulsed introduction of nitrogen intothe container both via individual nozzles and groups of nozzles or allthe nozzles projecting into the container.

[0024] The present invention is suitable, in particular, for use infoodstuff technology.

[0025] It is described by way of example below with reference to anexemplary embodiment illustrated in the diagrammatic drawing in which:

[0026]FIG. 1 shows a device according to the invention;

[0027]FIG. 2 shows a sectional front view of a nozzle; and

[0028]FIG. 3 shows a side view from the left of the nozzle according toFIG. 2.

[0029]FIG. 1 shows, by way of example, a device according to theinvention. A housing 1 comprises a container 2, in which, for example,two shafts 3 rotating in opposite directions during the cooling processare mounted. The centre points of the shafts 3 are marked by crosses andthe respective direction of rotation by arrows. Arranged on the shafts 3are mixing elements or mixing blades 4 which mix, blend, knead or grinda tough mass 5 of a, for example, meat-, tissue-, vegetable- and/orfruit-containing substance 5. The lower region of the container 2 ispreferably designed as a double trough 6, that is to say so as tocorrespond to an imaginary spatial surface formed by the mixing elements4 revolving in the container 2. Between the housing 1 and the container2 are arranged in each of the two sides at least one nozzle 7,preferably two nozzles, and, depending on the longitudinal extent of thedevice, in particular at least three or four nozzles.

[0030] The nozzles 7 preferably project at an angle of inclination βinto the trough region 6 of the container 2. A supply line 8 connectsthe nozzles 7 to a reservoir 9 for liquefied nitrogen (N₂) which, inthis state of aggregation, has a temperature lower than −196° C. and canbe obtained industrially in a very simple way, even in relatively largequantities, for example by air separation, that is to say by thefractionation of liquid air. The liquefied nitrogen is supplied to themass of a substance 5 at a constant working pressure via the nozzles 7.The liquid nitrogen advantageously brings about a very rapidthermodynamic exchange, in particular on the surface of the mass 5,which quickly becomes more brittle, so that clogging can be avoided andsubsequent further processing of the mass becomes easier.

[0031] The supply system 8 comprises a preferably horizontally arrangedstorage region 10 which can be locked hermetically by means of at leastone respectively preceding and following valve 11, 11 a, 11 b. The heatinsulation of the storage region 10 does not have to satisfy stringentrequirements. On the contrary, it is possible for the liquefied nitrogento evaporate partially in the storage region 10 by the supply of heatenergy, so that, by virtue of the different volumes of liquid andgaseous media, the pressure in the closed storage region 10 rises untila desired set pressure value is reached, the latter being detectedand/or indicated by a pressure device 12. Liquid and gaseous nitrogencan be separated in the storage region 10 by means of a diaphragm 13, inparticular for safety reasons. The storage region 10 may have aplurality of outlet points, so that variable pressure pulses can also bereleased: thus, the nozzles 7 can be supplied, in a pressure pulse lyingabove the working pressure, with a mixture of liquid and gaseousnitrogen via a supply portion 8 a and, for example, with liquid nitrogenalone via a supply portion 8 b.

[0032] The pressure device 12 and the valve 11 preceding the storageregion 10 or the valves 11 a, 11 b following the said storage region arepreferably connected to a regulating unit 20 which controls thecontinuous and/or pulsed introduction of nitrogen into the container 2via individual nozzles 7, groups of nozzles 7 and/or all the nozzles 7.In particular, the regulating unit 20 makes it possible to close thevalves 11, 11 a, 11 b and consequently hermetically enclose a definedquantity of liquefied nitrogen in the storage region 10 and also releaseit after build-up and the determination of a set pressure value via thepressure device 12.

[0033]FIG. 2 shows a sectional front view of a nozzle 7 installedpreferably in a device, as described above, for cooling a mass of asubstance. It can be seen clearly that the nozzle 7 has on thefluid-outlet side (illustrated on the right in FIG. 2) a conicalaperture angle α which advantageously also makes it easier to carry outa necessary blowing-out of deposits and/or icing-up in the flow duct 18of the nozzle 7. For reasons of fluid mechanics, the inlet region 19 ofthe nozzle 7 (on the left in FIG. 2) may also have a conical region a(not illustrated) which widens towards the base 14 of the nozzle 7. Thebase 14 also advantageously has, in addition to passage bores 15 forfastening the nozzles 7 to the housing 1, a retention aid 16, forexample likewise a passage bore 16, for the fault-free installation ofthe nozzle 7 on the device.

[0034] Alternatively or additionally to a conical aperture angle α, thenozzle 7 may have a specially configured surface 17 which is located onthe fluid-outlet side and which is designed to match with theabove-described spatial surface or contour of the trough 6.

[0035] Finally, FIG. 3 shows a side view from the left of the nozzle 7according to FIG. 2 or of its base 14.

[0036] The nozzle 7 preferably contains polytetrafluoroethylene (PTEF)which is advantageously suitable for use in foodstuff technology, in thesame way as the invention as a whole, in particular owing to lowadhesive forces, a low heat capacity and conductivity and, in general,its inert characteristic.

[0037] List of Reference Symbols List of reference symbols  1 Housing  2Container  3 Shafts  4 Mixing elements or mixing blades  5 Mass of asubstance  6 Trough or double trough  7 Nozzle  8, 8a, 8b Supply line  9Nitrogen reservoir 10 Storage region 11, 11a, 11b Valve 12 Pressuredevice 13 Diaphragm 14 Base 15 Passage bore 16 Retention aid 17 Surface,located on the fluid-outlet side, of the nozzle 7 18 Flow duct 19 Inletregion 20 Regulating unit

1-14: (canceled). 15: A method of cooling, comprising: a) providing amass to be cooled in a container, said mass comprising a substancecomprising at least one member selected from the group consisting of: i)meat; ii) tissue; iii) vegetable; and iv) fruit, said containercomprising a mixer, blender, or mill, said container comprising at leasttwo regions, including a lower region, and at least one nozzle; b)introducing liquefied nitrogen into said lower region at a constantworking pressure via said nozzle; and c) supplying said nitrogen bymeans of at least one pressure pulse during the cooling process orstoppage times, wherein said pulse comprises an increased pressure inrelation to said working pressure. 16: The method according to claim 15,wherein said pressure pulse is more than 4 times the working pressure.17: The method according to claim 16, wherein said pressure pulse ismore than 6 times the working pressure. 18: The method according toclaim 17, wherein said pressure pulse is more than 8 times the workingpressure. 19: The method according to claim 15, wherein said workingpressure is between about 1.5 and about 3.5 bar. 20: The methodaccording to claim 19, wherein said working pressure is between about 2and about 3 bar. 21: The method according to claim 20, wherein saidworking pressure is about 2.5 bar. 22: The method according to claim 15,wherein said pressure pulse is between about 16 and about 22 bar. 23:The method according to claim 22, wherein said pressure pulse is betweenabout 18 and about 20 bar. 24: The method according to claim 23, whereinsaid pressure pulse is about 19 bar. 25: The method according to claim15, wherein said pressure pulses are generated at regular timeintervals. 26: The method according to claim 25, wherein said pressurepulses are generated about every 4 to 6 minutes. 27: The methodaccording to claim 26, wherein said pressure pulses are generated aboutevery 5 minutes. 28: The method according to claim 15, wherein saidpressure pulses are generated as follows: a) hermetically enclosingliquid nitrogen under working pressure in a storage region, wherein saidstorage region comprises a heat transfer means; b) transferring heat viasaid heat transfer means, thereby evaporating part of said liquidnitrogen; c) increasing the pressure of said storage region, by virtueof different volumes of gaseous nitrogen and liquid nitrogen; and d)releasing in a pulsed manner liquid nitrogen or a mixture of liquid andgaseous nitrogen, when a desired set pressure value is reached. 29: Anapparatus for cooling a mass, comprising: a) a container comprising alower region and at least one nozzle; b) said container comprising amixer, blender or mill; c) said nozzle comprising a fluid-outlet side;d) a liquid nitrogen source fluidly connected to said container, saidliquid nitrogen source comprising a means for providing constantpressure; and e) means for providing at least one pressure pulse in saidliquid nitrogen during one or more of the cooling process or stoppagetimes, wherein said pulse comprises an increased pressure in relation tosaid working pressure. 30: The apparatus according to claim 29, furthercomprising a hermetically lockable storage region containing liquidnitrogen. 31: The apparatus according to claim 30, wherein said storageregion is part of a supply line attached to said nozzle. 32: Theapparatus according to claim 29, wherein said nozzle is comprised ofpolytetrafluoroethylene (PTEF). 33: The apparatus according to claim 29,wherein said fluid-outlet side comprises a conical aperture angle α ofbetween about 4° and about 12° relative to the centerline of saidnozzle. 34: The apparatus according to claim 33, wherein said conicalaperture angle α is between about 6° and about 10° relative to thecenterline of said nozzle. 35: The apparatus according to claim 34,wherein said conical aperture angle α is about 8° relative to thecenterline of said nozzle. 36: The apparatus according to claim 29,further comprising at least one mixing element rotatable in saidcontainer, said nozzle comprising a surface located on the fluid-outletside which is designed to match with a spatial surface formed by saidmixing element revolving in said container. 37: The apparatus accordingto claim 29, wherein a first gap is formed between said spatial surfaceformed by said rotating mixing elements and said surface of said nozzle,wherein said first gap is less than about 5 mm. 38: The apparatusaccording to claim 37, wherein said first gap is less than about 3 mm.39: The apparatus according to claim 38, wherein said first gap is lessthan about 1 mm. 40: The apparatus according to claim 37, wherein saidnozzle projects into said container at an angle of inclination β ofbetween about 4° and about 12° relative to a horizontal reference line.41: The apparatus according to claim 40, wherein said angle ofinclination β is between about 6° and about 10° relative to a horizontalreference line. 42: The apparatus according to claim 41, wherein saidangle of inclination β is less than about 8° relative to a horizontalreference line. 43: The apparatus according to claim 29, wherein saidmeans for providing said pressure pulse comprises individual nozzles,groups of nozzles, or all said nozzles. 44: An apparatus according toclaim 29, wherein said mass comprises at least one member selected fromthe group consisting of meat, tissue, vegetable, and fruit. 45: A methodof cooling, comprising: a) providing a mass to be cooled in a container,said mass comprising a substance comprising at least one member selectedfrom the group consisting of meat, tissue, vegetable, and fruit, saidcontainer comprising a mixer, blender, or mill, said containercomprising at least two regions, including a lower region, and at leastone nozzle; b) introducing liquefied nitrogen into said lower region ata constant working pressure via said nozzle; and c) supplying saidnitrogen by means of at least one pressure pulse during the coolingprocess or stoppage times, wherein said pulse comprises an increasedpressure in relation to said working pressure, wherein said workingpressure is about 2.5 bar, wherein said pressure pulse is more than 8times the working pressure, and wherein said pressure pulses aregenerated about every 5 minutes and are generated as follows: i)hermetically enclosing liquid nitrogen under working pressure in astorage region, wherein said storage region comprises a heat transfermeans; ii) transferring heat via said heat transfer means, therebyevaporating part of said liquid nitrogen; iii) increasing the pressureof said storage region, by virtue of different volumes of gaseousnitrogen and liquid nitrogen; and iv) releasing in a pulsed mannerliquid nitrogen or a mixture of liquid and gaseous nitrogen, when adesired set pressure value is reached.